Oscillator



Sept. 19, 1939.

H. O. PETERSON OSCILLATOR Filed Sept. 21, 1937 .S'YNCH.

INVENTOR. %05PE7'R50N ATTORNEY.

Patented Sept. 19, 1939 iiNi'iED STATES FATEN'E QFMQE OSCILLATOR tion of Delaware Application September 21, 1937, Serial No. 164,858

3 Claims.

This invention relates to an improved means for generating frequency oscillations.

More specifically, the present invention comprises a circuit and means whereby oscillations 5 having a saw-tooth wave form may be produced,

together with means whereby the frequency and the amplitude of the oscillations generated may be controlled.

Oscillations of saw-tooth wave form, that is, a wave form in which the voltage increases linearly and gradually to a predetermined amount and then decreases substantially instantaneously to the initial starting point are particularly useful in connection with television transmitting and receiving apparatuses wherein some form of a cathode ray tube is used to scan a picture area or to reproduce a picture on a fluorescent or luminescent screen. Oscillations of saw-tooth wave form are also used in cathode ray oscilloscopes and in fact may be employed in any instance where a stream of electrons is to be deflected for some purpose,

The particular advantage in using a saw-tooth Wave form in connection with a cathode ray tube for deflecting the stream of electrons generated therein, resides in the fact that the electron beam is caused to be deflected at a uniform rate in one direction, and is returned substantially instantaneously to the starting point for a subsequent deflection.

In systems wherein a cathode ray tube is used, it is almost invariably necessary that the frequency of the oscillations be maintained constant and that the frequency, as well as the Voltage, be adjustable in order that the rate of deflection as well as the amount of the deflection may be controlled, and it is, therefore, one purpose of the present invention to provide an oscillator for producing a saw-tooth Wave form wherein the frequency of oscillations may be controlled and, after the control is adjusted, the frequency will remain constant.

A further purpose of the present invention resides in the provision of means whereby the voltage of the saw-tooth wave form generated may be controlled.

Another purpose of the present invention is the provision of means whereby the saw-tooth Wave form will increase in voltage linearly and will decrease substantially instantaneously.

Still further purposes and advantages of the present invention will become more apparent to those skilled in the art from a reading of the following speciflcation and claims, particularly when considered in connection with the accompanying drawing, in which:

The figure is a schematic representation of a generator for producing oscillations having a saw-tooth wave form according to the present invention.

Referring to the drawing, an electron discharge tube I is provided which is generally known as a Kenotron and which comprises an electron emitter 3, and an anode i, Some means, such as a filament or heater 2 is provided for supplying the necessary thermal energy to the emitter 3. Such a tube may also be described as a diode or rectifier tube.

Connected to the heater element 2 are a source of current 6 and a variable resistance 5, as shown in the drawing. A source of anode potential I is also provided for maintaining the anode of the tube I sufficiently positive to attract the electrons emitted from the element 3. The negative terminal of the source of current I is connected to the emitter by way of a variable condenser 3. When the tube I is operated it is obvious that the discharge of current through the tube will cause an electrical charge to be accumulated upon the condenser 8.

A second discharge tube II] is also provided which preferably has the characteristics of a Thyratron and which comprises an electron emitter I I, a control electrode I2 and an anode I3. Means, such as a battery I4, is connected to the emitter or filament I I for supplying the necessary energy to produce an electron emission therefrom. The anode I3 is connected to the emitter of tube I while the emitter II of tube II! is connected to the negative terminal of the source of current I.

In order that the control electrode of tube It may be supplied with an appropriate biasing potential, a resistance I1 is connected in parallel with the tube and the control electrode is connected to some point along this resistance. In the connection is a source of current I5, the negative terminal of which is connected to the control electrode in order that at certain times the control electrode may be made negative with respect to the emitter II.

In the operation of the system so far described, the conduction of the Kenotron I causes a charge to be accumulated upon the condenser 6. In view of the characteristics of the tube I, the charge on the condenser 8 builds up gradually and linearly and, since the resistance I! is effectively in parallel therewith, the potential across this resistance accordingly increases. This increase continues until the control electrode I2 is made sumciently positive to permit the tube III to become conductive, When this point is reached, the impedance of the Thyratron I0 is very low and the condenser 8 is discharged through the tube Ill almost instantaneously. When this discharge takes place, the voltage across the resistance member I? likewise decreases and, because of the presence of the source of the current I5, the control electrode I2 again becomes negative and the Thyratron II] is rendered non-conductive and remains so until the condenser 8 is again charged,

As a result of this operation, a true saw-tooth Wave form or voltage is produced across the condenser 8.

The conductance of the Kenotron i may, of course, be controlled by varying the resistance 5 which in turn controls the amount of current which passes through the heater element 2. This adjustment naturally affects the frequency of the oscillations generated and a further control of the frequency may also be accomplished by varying the capacity of the condenser 8.

The amplitude of the voltage variation across the condenser 8 may be controlled by varying the amount of the negative bias 55 which is applied to the control electrode E2 of tube iii. The voltage or amplitude of the generated wave may also be varied by adjusting the point at which the control electrode is connected to the resistance iii. A further control of the voltage may be efiected by changing the voltage of the supply source i.

It may be seen, therefore, that a generator of a saw-tooth wave form oscillation has been provided, and, in view of the constant electronic output of the Kenotron i, the voltage of the wave form is built up in a straight line or linear manner. Furthermore, it may be seen that the frequency as well as the voltage of the oscillations may be controlled.

In order to utilize the system in connection with a cathode ray tube, a typical example of how the system may be connected to such a tube is shown. The cathode ray tube 2!] comprises the usual gun structure 2! for producing a stream of electrons. The electron stream is, of course,

rought to a focus by any well-known method or means and deflecting plates 22 and 23 are provided whereby the direction of movement of the beam may be controlled. As shown in the drawing, plates 22 are for the purpose of deflecting the electron beam in a horizontal direction whereas the plates 23 are for the purpose of deflecting the beam vertically. Assuming that it is desired that the cathode ray beam be deflected horizontally by the saw-tooth voltage generated by the oscillator, then the plates 22 are so connected that the voltage appearing across the condenser 8 will be impressed thereon. In order to simplify the drawing, one of the plates 22 is connected to ground as is also one plate of the condenser The other plate of the condenser is connected to the remaining one of the horizontal deflecting plates 22, and in this connection may be included a source of current 23 for the purpose of biasing the saw-tooth voltage oscillations in order that the position of the horizontal trav ersal or deflection of the cathode ray beam may be controlled. This battery may of course be made adjustable in order to laterally displace the cathode ray beam as desired. In systems wherein it is desired to maintain the oscillator in exact synchronism with another oscillator or in synchronism with another source of recurrent potential, and the synchronizing impulses may be connected to the conductor leading from the condenser 3 and one of the deflecting plates 22. In this connection is preferably inserted a small variable condenser 25. Although the frequency of oscillations of the oscillator described and shown herein is substantially fixed, it is, however, under certain circumstances desirable to definitely synchronize the oscillations with some external source of impulses and the present system is, therefore, readily adaptable to such use.

In the system shown, a small condenser I6 is connected between the anode E3 and the emitter ii of tube iii in order to by-pass and to prevent high frequencies which are sometimes inherently generated in the system from being radiated. This is done in order that frequency receiving apparatuses in the immediate vicinity of the oscillator will not be disturbed by these high frequency oscillations.

Although the oscillating system is shown as used in connection with a cathode ray tube, it is to be understood that the oscillations may be used in other respects where saw-tooth current or voltage variations are desired, and it is not necessary that such an oscillator be used specifically with cathode ray tubes.

It is further to be understood that although rather specific electron discharge tubes are shown and described, other tubes having similar characteristics but constructed in a different manner may well be used.

Various modifications and alterations may be made in the present invention without departing from the spirit and scope thereof, and it is intended that any and all such modifications be considered as within the purview of the present invention except as limited by the hereinafter appended claims.

I claim as my invention:

1. A system for generating a saw-tooth wave form comprising a discharge tube having at least a cathode and an anode, a condenser, source of current, means for connecting the positive terminal of the source of current to the anode of said tube, means for connecting one plate of said condenser to the cathode of said tube, means for connecting the negative terminal the source of current to the other plate of said condenser, a gas filled discharge tube having a cathode, a control electrode and an anode, means for connecting the anode and cathode of said gas filled tube to the one and the other plates of said condenser, a resistance connected in parallel with said condenser and means, including a second source of current, for connecting said control electrode to a point along said resistance.

2. A system for generating a saw-tooth wave form comprising a two element discharge tube, a condenser and a source of current, means for connecting said tube, condenser and source of current in series with the positive terminal of said current source connected to the anode of said tube, a gas filled discharge tube having a cathode, a control electrode and an anode, a resistance, means for connecting said resistance in parallel with said condenser, means for connecting the said cathode and anode across said condenser, and means including a second source of current for connecting said control electrode to a point along said resistance.

3. A system for generating a form comprising a diode having an anode and a cathode, a gas filled discharge tube having an anode, a control electrode and a cathode, means for connecting the cathode of said diode to the anode of said tube, means including a source of current for connecting the anode of said diode to the cathode of said tube, a condenser, means for connecting said condenser between the anode and cathode of said tube, a resistance, means including a source of current for connecting said control electrode to a point along said resistance, and means for connecting said resistance in parallel with said condenser.

saw-tooth wave HAROLD O. PETERSON. 

